The Arsonists still burns brightly

Morality play ... Ramin Gray and Benedict Cumberbatch in rehearsals for The Arsonists

The Arsonists is my title for a play previously known in this country as The Fire Raisers, first staged in Britain at the Royal Court in 1961. When Dominic Cooke and Ramin Gray asked me to come up with a new translation as part of the Court's international season, I went back to the original German text to see how much the play still had to say to a modern audience. In other words, I wondered whether I ought to be doing a straightforward translation or a new version. I was pleased to find that Max Frisch's famous play required little in the way of updating. In fact, apart from removing a few archaisms, I only took one major liberty with the text, replacing a traditional nursery rhyme with something more apposite to modern London.

The central character in The Arsonists is Biedermann, a man of contradictions. In his business life, he is brutal and unforgiving. In the domestic arena, he tries to live a life of blameless middle-class decency. This evokes echoes of all the monsters of history who spent their days torturing and murdering before going home to behave with impeccable correctness towards wife and children. It is this sense of bourgeois propriety that renders Biedermann defenceless when two arsonists turn up at his house.

The play itself is an extended metaphor about the weakness of personal ethics in the face of evil. Exactly what that evil is, Frisch never says, though as a Swiss citizen he felt keenly the stifling and hypocritical nature of middle-class morality. In the Royal Court production of 1961, director Lindsay Anderson cut to the chase and suggested that the evil in question was the atomic bomb.

We immediately have to ask: what is the great evil we are failing to face up to today? Is it still nuclear weapons? Is it the destruction of our environment through personal greed and corporate plunder? Is it the misery we inflict upon the Third World? Is it the erosion of our liberties in the name of the War on Terror? Is it the violence perpetrated on the people of Iraq? Is it Israel's cruel and illegal occupation of Palestine? Or could it be the threat to liberal values posed by radical Islam? With a Greek chorus composed of firefighters (as in the original), the play inevitably awakes memories of the London bombings of 2005, and if audiences want to engage with the issue of Islamism, this production certainly allows them to do that. But in the end, the power of The Arsonists lies in the undefined nature of the evil it portrays.

Where the play is precise is in identifying what happens when there is a private-public split in a person's moral code. When Biedermann finally realises that the men in his house really are arsonists, he is quite happy for them to go off and burn down someone else's house, not realising that he too will become one of the victims. What the play tells us is not that the liberal conscience is weak, but that the hypocritical liberal conscience is weak. We can't be decent people at home while ignoring the evils of the world. It just doesn't work.

· The Arsonists opens at the Royal Court Theatre London on November 6 2007. Previews begin tonight.